The present invention concerns bottom strips for tubular electrodes, for electric storage batteries. The invention likewise relates to electrodes provided with such bottom strips, and a process for manufacture of bottom strips and electrodes.
Tubular electrodes are used for various kinds of electric storage batteries, such as lead storage batteries and various alkaline batteries, for example. Each electrode comprises a plurality of rods with an outer tubular sheath of inert material that is permeable to the electrolyte. Within the sheath there is disposed electrochemically active electrode material, as well as one or more electric conductors, so-called cross bars. The cross bars are, as a rule, joined at the upper edge of the electrode with an electrically conductive strip, the so-called top frame. At the bottom, the tubular sheath is closed by a so-called bottom strip.
Manufacture of lead storage batteries proceeds in such a way that the cross pieces and the top frame are cast in one piece. The tubular sheath is then drawn over the cross bars, whereafter the electrode shell thereby produced is placed with the top frame downward and the tubular sheath is filled with active material. The sheath is closed thereafter with a bottom strip, generally made of a suitable plastic material.
The bottom strip can be fastened to the tubular sheaths, e.g., by being furnished with spurs that project into the tubes and are firmly pressed into them. The spurs may have recesses for the cross bars and thereby serve to center them. The bottom strip may also be glued or welded on. The bottom strip may be of solid or porous material.
The tubular sheaths can be made either as single tubes or cohesive so-called multiple tubes. In both cases, the fitting of the bottom strip may entail problems. There may be difficulty, particularly in the manufacture of lead storage battery electrodes, because the cross bars are made of relatively soft material. If the cross bars are intended to fit into a recess in the bottom strip spurs, but have become poorly centered in the course of filling, they can be bent by the bottom strip, as the latter is installed and forced out toward the side of the tube. In order to avoid this, it is necessary to check on the centering of the cross bars before the bottom strip is set on.
The above mentioned problems are solved by the present invention, and additional advantages are also attained in connection with the handling of the tubular sheaths and the charging of them with active material.